Reverse thermal gels and uses therefor

ABSTRACT

Biodegradable triblock copolymer compositions are provided which are useful in tissue engineering and drug delivery. The copolymers are reverse thermal gels in that when heated from a lower temperature to a higher temperature, they gel. These gels are useful in drug delivery when complexed with an active agent. For example the compositions can be used for intraocular injection of active agents, such as anti-angiogenic agents for treatment of a maculopathy or retinitis.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Nos.61/310,874, filed Mar. 5, 2010, 61/389,491, filed Oct. 4, 2010, and61/426,514, filed Dec. 23, 2010, each of which is incorporated herein byreference in its entirety.

STATEMENT REGARDING FEDERAL FUNDING

This invention was made with government support under the NationalInstitutes of Health Grant No. EB008565. The government has certainrights in this invention.

Provided herein are polymer compositions, methods of making polymercompositions, therapeutic products and methods of treating oculardiseases.

New and useful polymer compositions are desirable in the field ortreatment of diseases and conditions, and also for the repair of tissuedamage or insufficiencies (e.g., congenital), generally in the fields ofdrug delivery and regenerative medicine.

For example, human eyes are often exposed to various risks of oculardiseases. They can be an age-related such as macular degeneration;virulent inflammations by foreign bodies such as endophthalmitis; andsystemic side effects such as diabetic retinopathy, macular edema, andretinal vein occlusion. Delivery of therapeutic agents for oculartreatments can usually be limited by insufficient ocular uptake and sideeffects. The most prescribed conventional ocular dosage forms are eyedrops, eye ointments and suspensions. They have major disadvantages suchas poor bioavailability due to rapid precorneal elimination, normaltears turnover and conjunctiva absorption, frequent instillation ofconcentrated medication, side effects due to systemic absorption ofdrugs. Intravitreal drug injections are the most effective way tomaximize drug concentrations in the eye and reduce the loss whereaslimiting systemic exposure. However, the effective management of chronicocular conditions requires long-term frequent local administrations withover- and underdoses. Those repeated intravitreal injections are notonly invasive and inconvenient for patients, but they may also greatlyincrease the risk of complications such as intraocular pressureelevation, cataracts, and retinal detachment.

In another example, the failure to recover the functions of damagednerves may lead to severe conditions such as the malfunction of muscleand sensation. Although many studies on biomaterials for nerveregeneration have been reported, relatively little attention has beenpaid to the application of reverse thermal gelling copolymers that aregelled when temperature is above a threshold, especially those thatcarry functional groups. Injectable reverse thermal gelling biomaterialshave recently become highly desirable due to their unique advantages,including easy use and the minimally invasive procedures for the sitespecific introduction into the body relative to traditional surgicaltechniques. Moreover, when the final shape of the material is defined bythe local in vivo environment, such in situ-forming thermal gels areideal. Most of the early applications are based on Poloxamers fordelivery of protein/peptide drug, such as insulin, epidermal growthfactor, bone morphogenic protein, fibroblastic growth factor, andendothelial cell growth factor with sustained release kinetic overseveral hours. However, they have been proven to be toxic showing thatrats receiving 7.5 wt % of Poloxamers in their diet exhibited a decreasein growth rate.

SUMMARY

A novel copolymer composition that transitions from a copolymer solutionbelow a phase transition temperature to a gel above the phase transitiontemperature. As a non-limiting, but preferred example, the compositionis a liquid at room temperature and a gel at body temperature (e.g. 35°C.-40° C.), facilitating handling and delivery to a patient in aclinical setting. In such a case, the phase transition temperature rangeis about 25° C. to 40° C. It should be understood that phase transitionin these systems are dependent on other factors such as solutionconcentration even for the same material composition. Phase transitionthat starts at temperatures above 35° C. are useful in some instances,but given that phase transition is generally over a range of a fewdegrees, a composition having a phase transition temperature above 35°C. may not completely gel at body temperatures. Phase transitiontemperatures below 25° C. also are useful in some circumstances, butthose compositions may require refrigeration and cooling during transferto prevent the composition from gelling during delivery and thereforeare less practically useful than a composition with a phase transitiontemperature of from 28° C. to 30° C.

The reverse thermal gel has many uses, including as a drug deliverycomposition or dosage form. Active agents (e.g., drugs) or biologicallyfunctional groups (e.g., ECM epitope peptides and immune evasionpeptides), can be attached to, bound to or mixed into the copolymercomposition, and the composition can be delivered to a patient as aliquid at a temperature below the phase transition temperature of thecomposition. In certain embodiments, the active agents are one or moreof an antibiotic, an anti-inflammatory agent, an antiangiogenic agent, ahormone, a cytokine, a chemokine, and a growth factor. When placed in apatient, the temperature of the composition is raised, thereby forming ahydrogel. The copolymers described herein are biodegradable and erodewithin the patient, slowly releasing the active agent within thestructure. According to one non-limiting embodiment, the active agent isthe antiangiogenic agent, bevacizumab (AVASTIN). According to anotherthe active agent is MACUGEN pegaptanib sodium (MACUGEN). Or the activeagent can be Ranibizumab (Lucentis). As shown herein, a polymercomposition (PEG-Poly(serinol urethane)-PEG) comprising bevacizumab canprovide excellent long-term release profiles for vitreal injection totreatment of macular degeneration. Other active agents, such asantibiotics or anti-inflammatory compositions can likewise be deliveredto the eye.

Use of the compositions described herein is not limited to intra-oculardrug delivery. The compositions described herein can be used as cellgrowth scaffolds in vitro or in vivo. The compositions can beadministered to a patient either topically, or internally. For example,an open wound can be flushed with the composition and compressionapplied such that the gel warms and seals off the wound. The compositioncan also be administered internally, for instance by any parenteralroute, such as by injection by a syringe and needle, catheter, cannulaor trochar. The formation of a hydrogel within a patient is expected tobe able to stabilize internal damage and bleeding. As above, activeagents, including cytokines, chemoattractants, growth factors, epitopes,coagulating agents, antibiotics and anti-inflammatory agents may beincorporated into the composition to facilitate in the compositionserving a desired purpose. As illustrated below, the composition alsoshow promise as a nerve growth scaffold.

Methods of making the composition also are described below. Methods ofusing the composition, for delivery of an active agent, as a biologicalscaffold (e.g., cell growth scaffold), and as a wound treatment areprovided, as described below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 illustrate the synthesis of PEG-polyurethane (PU)-PEG andPEG-poly(ester urethane) (PEU)-PEG, respectively.

FIGS. 3A and 3B show FT-IR characterization of PEG-polyurethane (PU)-PEGand PEG-poly(ester urethane) (PEU)-PEG, respectively.

FIGS. 4A and 4B provide graphs showing thermal behavior ofPEG-polyurethane (PU)-PEG and PEG-poly(ester urethane) (PEU)-PEG,respectively.

FIG. 5 shows storage modulus changes of 30% (wt) PEG-PU-PEU solution.

FIG. 6 shows simulated concentration profile of therapeutic agents inthe vitreous fluid. (A) Proposed method that offers controlled releaseand a sustained concentration in the therapeutic range for a long periodafter one injection. (B) Current method that needs frequent injections.

FIG. 7 shows (Left) The device for the study of the controlled releaseof therapeutic agents. (Right) the detailed cross-sectional view of thecapsule as described in Example 2.

FIG. 8 provides 1H FTNMR spectra of poly (ethylene glycol)-poly(serinolhexamethylene urethane) (ESHU) in CDCl₃. The presence of a, e and gprotons indicate the presence of PEG, polyurethane and BOC-protectedamine groups in ESHU.

FIG. 9. Thermal behavior of ESHU. The solutions underwent temperaturetriggered sol (red)-gel (blue) phase transition and remained gels at 37°C. Inset shows images of the polymer solution at 3 stages correspondingto (from the bottom) sol, gel, and phase separation. (B) G′ changes withtemperature at 20 and 30% (wt) concentrations.

FIG. 10 is a graph showing in vitro degradation of ESHU in PBS and CEsolution. The degradation of ESHU was much faster in the presence of CE.Data are presented as means±S.D (n=3).

FIG. 11. In vitro cytotoxicity toward primary bovine corneal endotheliumcells. Phase images (100×) of Calcein AM treated cell morphologies of(A) control and (B) ESHU. No differences were observed between controland ESHU. Fluorescence images (100×) of cells of (C) control and (D)ESHU which stained with Hoechst and propidium iodide. Most nuclei (bluedots) are intact with a few red one.

FIG. 12 provides representative fluorescent photomicrographs (200×,scale bar=60 μm) of injection sites stained for ED1+ macrophages (red inoriginal). Tissues were harvested after: (A) 3 days; (B) 14 days, and(C) 28 days. (D) The number of ED I+ macrophages decreased with timeindicating a reduction in inflammatory response. **p<0.01 (pairedStudent's t-test).

FIG. 13 provides graphs showing the release profile of Avastin from ESHUgel. (A) With 0.5 mg of Avastin, 85.1% and 96.8%, and (B) with 1 mg,75.4% and 81.3% were released from 20% and 15% ESHU gels respectively at14 week post injection.

FIG. 14. 3D structure of IKVAVS-GEL.

FIG. 15. Phase contrast of cell morphology and neurite outgrowth onlaminin surface. (A) 1 day, (B) 7 days, (C) 14 days without RA, and (D)14 days with RA. Images were taken by the magnification of 100× for (A)and (B), and 200× for (C) and (D).

FIG. 16. Phase contrast of cell morphology and neurite outgrowth on purereverse thermal gel surface. (A) 1 day, (B) 7 days, (C) 14 days withoutRA, and (D) 14 days with RA. Images were taken by the magnification of100× for (A) and (B), and 200× for (C) and (D).

FIG. 17. Phase contrast of cell morphology and neurite outgrowth onIKVAVS-GEL surface. (A) 1 day, (B) 7 days, (C) 14 days without RA, and(D) 14 days with RA. Images were taken by the magnification of 100× for(A) and (B), and 200× for (C) and (D).

DETAILED DESCRIPTION

As used herein, the term “polymer composition” is a compositioncomprising one or more polymers. As a class, “polymers” includeshomopolymers, heteropolymers, co-polymers, block polymers, blockco-polymers and can be both natural and synthetic. Homopolymers containone type of building block, or monomer, whereas co-polymers contain morethan one type of monomer.

All ranges or numerical values stated herein, whether or not preceded bythe term “about” unless stated otherwise are considered to be precededby the term “about” to account for variations in precision ofmeasurement and functionally equivalent ranges.

As used herein, the terms “comprising,” “comprise” or “comprised,” andvariations thereof, are meant to be open ended. The terms “a” and “an”are intended to refer to one or more.

As used herein, the term “patient” or “subject” refers to members of theanimal kingdom including but not limited to human beings.

The term “alkyl” refers to both branched and straight-chain saturatedaliphatic hydrocarbon groups. These groups can have a stated number ofcarbon atoms, expressed as C_(x-y), where x and y typically areintegers. For example, C₅₋₁₀, includes C₅; C₆, C₇, C₈, C₉, and C₁₀.Alkyl groups include, without limitation: methyl, ethyl, propyl,isopropyl, n-, s- and t-butyl, n- and s-pentyl, hexyl, heptyl, octyl,etc. Alkenes comprise one or more double bonds and alkynes comprise oneor more triple bonds. These groups include groups that have two or morepoints of attachment (e.g., alkylene). Cycloalkyl groups are saturatedring groups, such as cyclopropyl, cyclobutyl, or cyclopentyl. Aromaticgroups include one or more benzene rings. As used herein, “halo” or“halogen” refers to fluoro, chloro, bromo, and iodo. An amine is a grouphaving the structure —N(R1)(R2). Where R1 and R2 are H, the group isamino.

A polymer “comprises” or is “derived from” a stated monomer if thatmonomer is incorporated into the polymer. Thus, the incorporated monomerthat the polymer comprises is not the same as the monomer prior toincorporation into a polymer, in that at the very least, certainterminal groups are incorporated into the polymer backbone or areremoved in the polymerization process. A polymer is said to comprise aspecific type of linkage if that linkage is present in the polymer.

The polymers described herein are said to be bioerodible orbiodegradable. By that, it is meant that the polymer, once implanted andplaced in contact with bodily fluids and tissues, or subjected to otherenvironmental conditions, such as composting, will degrade eitherpartially or completely through chemical reactions, typically and oftenpreferably over a time period of hours, days, weeks or months.Non-limiting examples of such chemical reactions include acid/basereactions, hydrolysis reactions, and enzymatic cleavage. The polymersdescribed herein contain labile ester linkages. The polymer or polymersmay be selected so that it degrades over a time period. Non-limitingexamples of useful in situ degradation rates include between 12 hoursand 5 years, and increments of hours, days, weeks, months or yearstherebetween. For example, in the context of an drug product to beinjected via the intravitreal route, the polymer may preferably degradeover 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 months, or longer.

Provided is a reverse thermal gel composition comprising a triblockcopolymer having the structure B-A-B in which A is one of a polyurethaneor poly(ester urethane) group that comprises one or more pendant activegroups, blocked active groups or active agents and B is a hydrophilicblock that can be PEG of various sizes, hyaluronan of various sizes,poly(vinyl alcohol) or oligo(vinyl alcohol), polycarbohydrage, etc.Examples of poly(ethylene glycol) average molecular weights include 350,550, 750, 1000, and 1900 Da. The composition is in solution at a lowertemperature, e.g., at room temperature and transitions to a gel as thetemperature is raised, to form a complete gel at a higher temperature,e.g., physiological (body) temperature (e.g., 35° C.-40° C.). Thetransition temperature also may be referred to as the Lower CriticalSolution Temperature, or LCST) is preferably 30° C. or less or 25°C.-30° C. As an example, the transition point is above room temperature(RT, for example 25° C.) and physiological temperature (typically 37° C.but there can be individual differences). As a further example, thecomposition begins transformation as the temperature rises from 25° C.and forms a gel around 33-35° C. and still remains gel at 37° C. Thetriblock copolymer may be converted to a pharmaceutically acceptablesalt. In one embodiment, A is a copolymer of a diol (a hydrocarboncomprising aliphatic or aromatic groups and which may be saturated orunsaturated) and a diisocyanate. The diol may be amino-substituted orN-substituted serinol, such as N-boc serinol, in which the N issubstituted with one of a hydrogen, a protective group (a removablegroup that prevents the amine or other desirable moiety from reactingduring synthesis of the triblock copolymer), or an active agent. Inanother embodiment, the N of the N-substituted serinol is —NHR in whichR is a protective group, such as carbobenzyloxy; p-methoxybenzylcarbonyl; tert-butyloxycarbonyl; 9-fluorenylmethyloxycarbonyl; benzyl;p-methoxybenzyl; 3,4-dimethoxybenzyl; p-methoxyphenyl; tosyl; nosyl(4-nitrobenzenesulfonyl) and 2-nitrobenzenesulfonyl.

In another embodiment, the diol comprises one or more ester groups, aswhen it is a reaction product of a cyclic anhydride and a diolcomprising one or more pendant active groups, blocked active groups oractive agents. For example, the diol in one particular embodiment is thereaction product of succinic anhydride and an N-substituted serinol inwhich the N is substituted with one of a hydrogen, a protective group,such as carbobenzyloxy; p-methoxybenzyl carbonyl; tert-butyloxycarbonyl;9-fluorenylmethyloxycarbonyl; benzyl; p-methoxybenzyl;3,4-dimethoxybenzyl; p-methoxyphenyl; tosyl; nosyl(4-nitrobenzenesulfonyl) and 2-nitrobenzenesulfonyl, or an active agent.In one embodiment, the diol comprises a pendant amino group or an amine.One example of a diisocyanate is hexamethylene diisocyanate(1,6-diisocyanatohexane).

According to one embodiment, the composition comprises a copolymercomprising the structure:

in which R1 is H or a protective group, R2 is isocyanate or —NC(O)—PEGand n is greater than 5, for example and without limitation, 8-30, 8-25or 18-30.According to another embodiment, the composition comprises a copolymercomprising the structure:

in which R1 is H or a protective group or an active agent, R2 isisocyanate or —NC(O)—PEG and n is greater than 5, for example andwithout limitation, 8-30, 8-25 or 18-30.

In one embodiment, the triblock copolymer has an average molecularweight of between about 3,000-50,000 Da (Daltons), for instance between5,000 and 10,000 Da, excluding, when present, the molecular weight ofthe active agent. The composition may comprise an active agent complexed(non-covalently bound) to a triblock copolymer as described above.According to one non-limiting embodiment, the active agent is theantiangiogenic agent, bevacizumab (AVASTIN). According to another theactive agent is MACUGEN pegaptanib sodium (MACUGEN).

Also provided is a method of delivering an active agent to a patient,comprising delivering to the patient a reverse thermal gel compositioncomprising an active agent and a triblock copolymer having the structureB-A-B in which A is one of a polyurethane or poly(ester urethane) groupthat comprises one or more pendant active groups, blocked active groupsor active agents and B is a poly(ethylene glycol) and which is a gel at37° C. and a liquid at a temperature below 30° C. In one embodiment, theactive agent is an antiangiogenic agent, such as bevacizumab. Thecomposition may be any composition described above, for example acomposition comprising a triblock copolymer chosen from one of:

in which R1 is H and R3 is PEG, and which is complexed with anantiangiogenic agent, such as bevacizumab.

In another embodiment, a method of treating a wound or defect in apatient is provided, comprising delivering to a site in or on thepatient a reverse thermal gel composition as described herein. Where thesite in the patient is internal, the composition is delivered by aneedle, cannula, catheter, trochar or any similar devices.

According to another embodiment, a method of making a triblock copolymeris provided. The method comprises: reacting a diol with a diisocyanateto produce a diol product; and PEGylating the diol product. In oneembodiment, the idol is synthesized by reacting a diol precursor with acyclic anhydride. An example of a diol precursor is N-serinol in whichthe N is substituted with a protective group, such as Boc such that thediol precursor is N-boc-serinol. In another embodiment, the cyclicanhydride is succinic anhydride. Any embodiment of these methods mayfurther comprise complexing the triblock copolymer with an active agent.In one embodiment, the diol precursor is N-serinol, in which the N issubstituted with a protective group, for instance N-boc serinol. In yetanother embodiment, the diisocyanate is hexamathylene diisocyanate.

The polymer compositions may be modified to include biologically activegroups or active agents either covalently bound (attached) to thepolymer structure or bound to the structure non-covalently. Activeagents can be admixed with the polymer composition, absorbed or adsorbedinto the composition. Active agents that may be incorporated into thecompositions described herein include, without limitation,anti-inflammatories, such as, without limitation, NSAIDs (non-steroidalanti-inflammatory drugs) such as salicylic acid, indomethacin, sodiumindomethacin trihydrate, salicylamide, naproxen, colchicine, fenoprofen,sulindac, diflunisal, diclofenac, indoprofen sodium salicylamide,antiinflammatory cytokines, and antiinflammatory proteins or steroidalanti-inflammatory agents); antibiotics; anticlotting factors such asheparin, Pebac, enoxaprin, aspirin, hirudin, plavix, bivalirudin,prasugrel, idraparinux, warfarin, coumadin, clopidogrel, PPACK, GGACK,tissue plasminogen activator, urokinase, and streptokinase; growthfactors. Other active agents include, without limitation: (1)immunosuppressants; glucocorticoids such as hydrocortisone,betamethisone, dexamethasone, flumethasone, isoflupredone,methylpred-nisolone, prednisone, prednisolone, and triamcinoloneacetonide; (2) antiangiogenics such as fluorouracil, paclitaxel,doxorubicin, cisplatin, methotrexate, cyclophosphamide, etoposide,pegaptanib, lucentis, tryptophanyl-tRNA synthetase, retaane, CA4P,AdPEDF, VEGF-TRAP-EYE, AG-103958, Avastin, JSM6427, TG100801, ATG3,OT-551, endostatin, thalidomide, becacizumab, neovastat; (3)antiproliferatives such as sirolimus, paclitaxel, perillyl alcohol,farnesyl transferase inhibitors, FPTIII, L744, antiproliferative factor,Van 10/4, doxorubicin, 5-FU, Daunomycin, Mitomycin, dexamethasone,azathioprine, chlorambucil, cyclophosphamide, methotrexate, mofetil,vasoactive intestinal polypeptide, and PACAP; (4) antibodies; drugsacting on immunophilins, such as cyclosporine, zotarolimus, everolimus,tacrolimus and sirolimus (rapamycin), interferons, TNF binding proteins;(5) taxanes, such as paclitaxel and docetaxel; statins, such asatorvastatin, lovastatin, simvastatin, pravastatin, fluvastatin androsuvastatin; (6) nitric oxide donors or precursors, such as, withoutlimitation, Angeli's Salt, L-Arginine, Free Base, Diethylamine NONOate,Diethylamine NONOate/AM, Glyco-SNAP-1, Glyco-SNAP-2,(.+−.)-S-Nitroso-N-acetylpenicillamine, S-Nitrosoglutathione, NOC-5,NOC-7, NOC-9, NOC-12, NOC-18, NOR-1, NOR-3, SIN-1, Hydrochloride, SodiumNitroprusside, Dihydrate, Spermine NONOate, Streptozotocin; and (7)antibiotics, such as, without limitation: acyclovir, afloxacin,ampicillin, amphotericin B, atovaquone, azithromycin, ciprofloxacin,clarithromycin, clindamycin, clofazimine, dapsone, diclazaril,doxycycline, erythromycin, ethambutol, fluconazole, fluoroquinolones,foscarnet, ganciclovir, gentamicin, iatroconazole, isoniazid,ketoconazole, levofloxacin, lincomycin, miconazole, neomycin,norfloxacin, ofloxacin, paromomycin, penicillin, pentamidine, polymixinB, pyrazinamide, pyrimethamine, rifabutin, rifampin, sparfloxacin,streptomycin, sulfadiazine, tetracycline, tobramycin, trifluorouridine,trimethoprim sulphate, Zn-pyrithione, and silver salts such as chloride,bromide, iodide and periodate.

Active agents that may be bound to the polymer composition includepeptides (e.g., ECM epitopes) for functionalizing the gel with abiologically functional group. Useful peptides include or consist of thefollowing amino acid sequences: IKLLI (SEQ ID NO: 1)(anti-apoptotic),REDV (SEQ ID NO: 2), LDV, RGDSP (SEQ ID NO: 3), RGDV (SEQ ID NO: 4),LRGDN (SEQ ID NO: 5), RGDT (SEQ ID NO: 6), YIGSR (SEQ ID NO: 7), TTSWSQ(SEQ ID NO: 8), AEIDGIEL (SEQ ID NO: 9), WYRGRL (SEQ ID NO: 10), SIKVAVS(SEQ ID NO: 11), PDSGR (SEQ ID NO: 12), RNIAEIIKDI (SEQ ID NO: 13), DGEA(SEQ ID NO: 14), VTXG (SEQ ID NO: 15), PRRARV (SEQ ID NO: 16),YEKPGSPPREVVPRPRPGV (SEQ ID NO: 17), RPSLAKKQRFRHRNRKGYRSQRGHSRGR (SEQID NO: 18), RIQNLLKITNLRIKFVK (SEQ ID NO: 19), RGD, IKVAV (SEQ ID NO:20) and IKVAVS (SEQ ID NO: 21). In one example, these oligopeptides arelinked via their amine groups to the polymeric structures describedherein. In another embodiment, biomolecules are attached or bound to thepolymer composition which aid in evasion of an immune response.Non-limiting examples of such peptides are: betaine, derivatives ofbetaine, and other zwitterionic groups including certain amino acids andtheir derivatives.

The active agent or any compound or composition may be bound to thepolymer in any useful manner, for instance: covalently (including bycoordination and by use of a suitable linkers and linking methods as arebroadly known and are broadly available in the art, for example linkersand methods of use of linkers are commercially available from ThermoFisher Scientific, Pierce Protein Research Products, Rockford, Ill., seealso Thermo Scientific Pierce Crosslinking Technical Handbook, 2009Thermo Fisher Scientific Inc.), by affinity or charge (that is,non-covalently), or by intermixing with the polymer when the compositionis in solution phase. Binding of the active agent or any compound orcomposition by affinity or charge, e.g., by polar, hydrogen bonding,charge (ionic/electrostatic), or van der Waals interactions, may bepreferred in many instances because the compound is not free to diffuseprior to or after gelation, as in the case of the active agent beingintermixed with the polymer in the composition, or is not covalentlymodified, which can hamper efficacy of the active agent.

In one embodiment, the active agent is used for prevention or treatmentof an ocular disease (disorder or condition), such as a maculopathy, aretinopathy, glaucoma, an inflammatory condition, a bacterial infection,a viral infection or a wound. The composition comprising the activeagent is delivered to the eye in any useful fashion. In order to ensureconsistent delivery, in one embodiment, the composition is delivered byintravitreal injection. In that case, the composition slowly breaks downin the vitreous humor and the drug is released as the composition breaksdown. Suitable active agents include without limitation: antibiotics,anti-inflammatory agents, analgesics, antiangiogenic agents, and growthfactors.

Non-limiting examples of antiangiogenic agents include: Macugen(pegaptanib sodium); Lucentis; Tryptophanyl-tRNA synthetase (TrpRS);AdPEDF; VEGF TRAP-EYE; AG-013958; Avastin (bevacizumab); JSM6427;TG100801; ATG3; Perceiva (originally sirolimus or rapamycin); E10030,ARC1905 and colociximab (Ophthotech) and Endostatin. Ranibizumab iscurrently the standard in the United States for treatment of neovascularAMD. It binds and inhibits all isoforms of VEGF. Although effective inmany cases, treatment with ranibizumab requires sustained treatmentregimens and frequent intravitreal injections. VEGF Trap is a receptordecoy that targets VEGF with higher affinity than ranibizumab and othercurrently available anti-VEGF agents. Blocking of VEGF effects byinhibition of the tyrosine kinase cascade downstream from the VEGFreceptor also shows promise, and includes such therapies as vatalanib,TG100801, pazopanib, AG013958 and AL39324. Small interfering RNAtechnology-based therapies have been designed to downregulate theproduction of VEGF (bevasiranib) or VEGF receptors (AGN211745). Otherpotential therapies include pigment epithelium-derived factor-basedtherapies, nicotinic acetylcholine receptor antagonists, integrinantagonists and sirolimus. (See, e.g., Chappelow, A V, et al.Neovascular age-related macular degeneration: potential therapies,Drugs. 2008; 68(8):1029-36 and Barakat M R, et al. VEGF inhibitors forthe treatment of neovascular age-related macular degeneration, ExpertOpin Investig Drugs. 2009 May; 18(5):637-46.

An anti-inflammatory agent may be administered in an amount effective todecrease ocular inflammation and pain associated with a given condition.Steroidal anti-inflammatories are useful, but not preferred because theycan cause corneal thinning. Non-steroidal anti-inflammatories (NSAIDs)suitable for ocular use are preferred and include, without limitation:nepafenac (for example and without limitation, Nevenac 0.1%, nepafenacophthalmic suspension, Alcon Laboratories, Inc.), ketorolac tromethamine(for example and without limitation, Acular LS 0.4%, ketorolactromethamine ophthalmic suspension, Allergan, Inc.), acetaminophen andbromfenac (for example and without limitation, Xibrom 0.09%, bromfenacophthalmic suspension, Ista Pharmaceuticals). Thus, also provided hereinis a composition comprising the described block copolymer and apharmaceutically acceptable anti-inflammatory suitable for optical use.These anti-inflammatory compounds often exhibit analgesic effects. Inany case, according to the methods described herein, the binding reagentand the anti-inflammatory may be contained in the same composition, butalso may be administered separately in a manner effective to treat theinfection.

An antibiotic also may be administered along with the block copolymerand, optionally, the anti-inflammatory agent may also be co-administeredwith the antibiotic, all in an amount effective to treat and/or preventinfection and/or its symptoms. Non-limiting examples of suitableantibiotics include: ciprofloxacin, norfloxacin, afloxacin,levofloxacin, gentamicin, tobramycin, neomycin, erythromycin,trimethoprim sulphate, and polymixin B. Antiviral compounds also may beadministered in this manner, such as ganciclovir or fomivirsen.

In any case, as used herein, any active agent used for prevention ortreatment of a condition, such as, for example, a maculopathy, such asage-related macular degeneration, diabetic retinopathy, or ocularinfection, is administered in an amount effective to treat or preventthat condition, namely in an amount and in a dosage regimen effective toprevent or reduce the duration and/or severity of the condition. As anexample, between 1 and 500 mg, for example from 1.25 and 60 mg ofAVASTIN (bevacizumab) can be administered in one intravitreal injectionwhen mixed with the block copolymer. The actual amount of active agentpresent in the composition will depend on the degradation rate of thecopolymer and dissociation rate of the agent from the composition. Theordinary intraocular injection dose for AVASTIN is 1.25-2.5 mg permonth. If the gel degrades over 6 months, the amount in each “gel” dosewould contain 7.5-15 mg AVASTIN, 15-30 mg if the composition degradesover a year. Different concentrations and specific activities of activeagents will achieve similar results. The composition (drug product) maybe administered once or more than once, depending on the duration of theerosion of the block copolymer. For example, the composition can beadministered monthly, bimonthly, quarterly or yearly. The amount (e.g.,number of drops of drug product) of the drug product administered to thepatient, also may vary though the amount administered should not beeither harmful to the patient or interfere other than insubstantiallywith functioning, such as vision.

Non-limiting examples of growth factors suitable for ocular use include:non-mitogenic human acidic fibroblast growth factor (nm-haFGF),neurotrophin nerve growth factor (NGF), epidermal growth factors (EGF),brain-derived neurotrophic factor (BDNF), glial cell line-derivedneurotrophic factor (GDNF), neurotrophin-3 and eye-derived growthfactor(s) (EDGF).

In one embodiment, a combined dosage form is provided comprising two ormore of an anti-angiogenic agent, an anti-inflammatory agent, anantibiotic agent and a growth factor. For example, either an antibioticor antiviral agent may be co-administered with an anti-inflammatoryagent.

In any use for the prevention and/or treatment of any condition in apatient, a person of ordinary skill in the pharmaceutical and medicalarts will appreciate that it will be a matter of simple design choiceand optimization to identify a suitable dosage regimen for treatment ofany given condition using the delivery systems/compositions describedherein. As such, the composition may comprise a carrier, such as anopthamologically-acceptable carrier, which comprises acceptableexcipients, such as, without limitation, one or more suitable:vehicle(s), solvent(s), diluent(s), pH modifier(s), buffer(s), salt(s),colorant(s), rheology modifier(s), lubricant(s), antifoaming agent(s),hydrogel(s), surfactant(s), emulsifier(s), adjuvant(s), preservative(s),phospholipid(s), fatty acid(s), mono-, di- and tri-glyceride(s) andderivatives thereof, wax(es), oil(s) and water, as are broadly known inthe pharmaceutical arts.

The compositions described herein may find use as cell growth scaffolds.Cells may be microintegrated within a cell growth matrix using a varietyof methods. In likely the simplest embodiment to implement, the cellsare mixed with the copolymer when it is a miscible liquid, below thegelation temperature. The following are examples of methods used toincorporate cells into traditional cell scaffolds that are gelled orsolid at the time of cell incorporation. They may be useful in casewhere a cell type would need to be preconditioned to the matrix prior toimplantation. In the context of the present disclosure, the gel may bewarmed until it gels and then cells are incorporated, for example, asfollows. In each case, the gel would need to be kept above the gelationtemperature throughout. However, reduction of the temperature until thegel/cell mixture is a miscible liquid may be desirable for the purposeof either facilitating delivery to a patient through a needle orcatheter, or for isolating cells, in that the solution can becentrifuged to pellet the cells.

In one example, a gel is submersed in an appropriate growth medium forthe cells to be incorporated, and then directly exposed to the cells.The cells are allowed to proliferate on the surface and interstices ofthe matrix. The matrix is then removed from the growth medium, washed ifnecessary, and implanted. Cells of interest also can be dissolved intoan appropriate solution (e.g., a growth medium or buffer) and thensprayed onto a growth matrix. This method is particularly suitable whena highly cellularized tissue engineered construct is desired. In oneembodiment, pressure spraying (i.e., spraying cells from a nozzle underpressure) is used to deposit the cells. In another, the cells areelectrosprayed onto the non-woven mesh during electrodeposition.Electrospraying involves subjecting a cell-containing solution with anappropriate viscosity and concentration to an electric field sufficientto produce a spray of small charged droplets of solution that containcells.

Many cell types require a support cell population or matrix in order to,for example, survive, grow, propagate or differentiate. As indicatedabove, cells can be mixed with the composition at a temperature belowthe gelation temperature for the composition. Next, the temperature ofthe composition is raised to produce a gel containing the cells. Thecells are grown at a temperature at which the composition is gelled.Lastly, the cells can be removed from the gel by first lowering thetemperature of the composition to below the gelation temperature to“melt” the gel, and then the cells are washed, e.g., with medium, salineor PBS (Phosphate-Buffered Saline) to remove the polymer composition. Bythis method specific shapes of tissue may be generated, for instance bygrowing the cells in a mold, and letting the cells grow/differentiateuntil cell-cell interaction is achieved. Once the cells or tissue isgrown, the cells or tissue can then be washed free of any remainingpolymer.

The cells that may be incorporated on or into the gel includes stemcells such as adipose or neural stem cells; progenitor (precursor)cells; smooth muscle cells; skeletal myoblasts; myocardial cells;endothelial cells; endothelial progenitor cells; bone-marrow derivedmesenchymal cells and genetically modified cells. In certainembodiments, the genetically modified cells are capable of expressing atherapeutic substance, such as a growth factor. Examples of suitablegrowth factors include angiogenic or neurotrophic factor, whichoptionally may be obtained using recombinant techniques. Non-limitingexamples of growth factors include basic fibroblast growth factor (bFGFor FGF-2), acidic fibroblast growth factor (aFGF), nerve growth factor(NGF), vascular endothelial growth factor (VEGF), hepatocyte growthfactor (HGF), insulin-like growth factors (IGF), transforming growthfactor-beta pleiotrophin protein, midkine protein.

In one embodiment of the methods described herein, the composition, withor without cells, growth factors, active agents, etc. is injected ordeposited at the site of a wound to heal the wound. Wrapping or coveringthe wound, e.g., in bandages can insure that the composition remains ata temperature at which it is a gel. The composition with or withoutcells, growth factors, active agents, etc., can be injected or otherwiseadministered at any point in or on a patient. For instance a catheter,cannula, trochar, syringe, etc. can be used to deliver the compositionto a desired location. In one embodiment, a method of growing nervecells, such as a method of repairing a nerve, is provided. In oneembodiment, the composition is implanted in a wound to a nerve so thatnerve cells can populate the hydrogel and nerve structure and functionis regenerated. For example, the composition can be implanted at a siteof a spinal cord wound (see below for an example) and the nerve tissueis regenerated.

Pharmaceutically acceptable salts are, because their solubility in wateris greater than that of the initial or basic compounds, particularlysuitable for medical applications. These salts have a pharmaceuticallyacceptable anion or cation. Suitable pharmaceutically acceptable acidaddition salts of the compounds of the invention include, withoutlimitation, salts of inorganic acids such as hydrochloric acid,hydrobromic, phosphoric, metaphosphoric, nitric and sulfuric acid, andof organic acids such as, for example, acetic acid, benzenesulfonic,benzoic, citric, ethanesulfonic, fumaric, gluconic, glycolic,isethionic, lactic, lactobionic, maleic, malic, methanesulfonic,succinic, p-toluenesulfonic and tartaric acid. Suitable pharmaceuticallyacceptable basic salts include without limitation, ammonium salts,alkali metal salts (such as sodium and potassium salts), alkaline earthmetal salts (such as magnesium and calcium salts), and salts oftrometamol (2-amino-2-hydroxymethyl-1,3-propanediol), diethanolamine,lysine or ethylenediamine. Pharmaceutically acceptable salts may beprepared from parent compounds by any useful method, as are well knownin the chemistry and pharmaceutical arts.

As described above, the compositions described herein are useful fordrug delivery, especially were systemic treatment is not necessary ordangerous. One or more therapeutic agents may be included in thecompositions and the composition is delivered to a site in a patient,where the composition gels. Delivery of the composition is limited bythe rate of degradation of the polymeric component of the composition.As such, the composition may be useful in treating tumors, for example,by complexing an anticancer agent with the polymeric component of thecomposition and delivering the composition to the site of a tumor, whereit slowly releases the anticancer agent. Likewise, these compositionsmay find use in treating localized conditions, such as abcesses. Thecomposition may be useful in delivering steroids at a constant rate, forexample in the case of testosterone, where less than optimal injections,topical gels and patches are the norm, or contraceptives.

Example 1

This study aims to develop injectable reverse thermal gelling triblockcopolymers with serinol-derived polyurethane (PU) and polyester urethane(PEU) and study its potential as nerve regenerative matrices. PUs areuseful materials in biomedical fields since they have been proven to bebiocompatible. (Zdrahala, R. J.; Zdrahala, I. J. J. Biomater. Appl.1999, 14, 67-90). They are easily tailored by changing hard segmentchemistries and concentrations leading to the intended functions. (Tang,Y. W.; Labow, R. S.; Santerre, J. P. Journal of Biomedical MaterialsResearch 2001, 57, 597-611 and Tang, Y. W.; Labow, R. S.; Santerre, J.P. J. Biomed. Mater. Res. 2001, 56, 516-528). The applications of PUshave been extended to catheters, compliant vascular grafts, andprosthetic valve leaflets since the first introduction as materials forbreast prostheses.

Thus, the incorporation of biocompatible PUs with serinol and PEGresulting in functionalized injectable reverse thermal gellingcopolymers will be the breakthrough in the field of tissue engineering,especially in the nerve regeneration.

Synthesis of Thermal Gelling Copolymers

In first step, two types of thermal gelling copolymers, PEG-polyurethane(PU)-PEG and PEG-poly(ester urethane) (PEU)-PEG, were designed (SeeFIGS. 1 and 2). PU was synthesized using N-BOC-serinol and hexamethylenediisocyanate (HDI) at 90° C. The attachment of PEG was performed by theformation of urethane bonds with HDI. PEU was synthesized in two steps.First, the esters were synthesized using N-BOC-serinol and succinicanhydride at 90° C. Then the as-synthesized esters reacted with HDI at90° C. to make PEU followed by PEG attachment.

The PEG-PU-PEG was characterized by FT-IR (FIGS. 3A and 3B which showedbands of C═N by HDI and C═O by urethane bonds at 2270 and 1650-1680 cm⁻¹respectively. The C═N peak disappeared after the PEG attachment whereasether, R—O—R, signal by PEG appeared at 1000-1150 cm⁻¹. For thesynthesis of PEG-PEU-PEG, the bands of C═N by HDI, C═O by urethane andester bonds, and R—O—R by PEG in PEU appeared at 2270, 1600-1750, and1000-1150 cm⁻¹, respectively.

Thermal Behavior of Copolymers

The phase transition from solution to gel largely depends on the balanceof hydrophilic (PEG) and hydrophobic (PU, PEU) portions in copolymerstructures. In addition, by modulation of the length of hydrophobicparts the gelling temperature can be adjusted. Based on these facts wedeveloped specifically designed thermal gelling copolymers with phasetransition at physiologically important temperature range of 32-37° C.The storage modus (G′) of the polymer solutions in PBS solution wasmeasured by rheometer from 20° C. to 55° C.

The thermal behavior showed that the aqueous polymer solution ofPEG-PU-PEG prepared with 30 and 40% (wt) concentrations started phasetransition from 31-32° C. and remained gel in the temperature range of37-40° C. For the aqueous solution of PEG-PEU-PEG, they remained gel inthe temperature range of 35-37° C. with all concentrations tested (FIGS.4A and 4B). The implication of these graphs are that the compositions,with an increase in temperature will solidify, so long as theconcentration of the polymer in solution is above a minimalconcentration as shown in FIGS. 4A and 4B. For example, forPEG-PSeHDI-PEG, for concentrations between about 8% (wt) and 50% (wt),the composition is a solution at low temperatures, such as below about32% (wt), and phase separation occurs at a higher temperature, such asat about 38° C. for a 30% (wt) solution of the copolymer. Thus, fortypical uses in humans, a temperature range at which the composition ispreferably a gel is, for example, between 32-40° C. or 32-38° C.,meaning the concentration of the copolymer may be preferably between 20%(wt) to 50% (wt). For PEG-PSeSuHDI-PEG, the concentration of thecopolymer may be preferably between 15% (wt) to 50% (wt).

FIG. 5 shows storage modulus changes of 30% (wt) PEG-PU-PEU solution. Nosignificant changes of the storage modulus (G′) were observed until 31°C. indicating that it remained fluidic; a dramatic increase in thestorage modulus were observed between 32-36° C. indicating the gelation,and the decrease in modulus occurred showing the phase separation.

Degradation of PEG-PU-PEG and PEG-PEU-PEG

For biodegradability, the copolymer solution was treated with both PBSsolution and cholesterol esterase, and the molecular weights weremeasured every 7 days for 2 weeks. Each polymer was dissolved in bothPBS solution and 400 U/ml of enzyme solutions with concentration of 5%(wt). 0.2 ml of fresh enzyme solution (2,000 U/ml) was added every threedays to recover the enzyme activity.

The PEG-PU-PEG incubated in PBS solution did not show Mw changes whereas3.4% decrease in Mw was observed in enzyme solution in two weeks. Forthe PEG-PEU-PEG, 5.2% decrease in Mw was observed even in PBS solution.Much higher decrease in Mw, 29.8%, was observed in enzyme solution. Thusboth PEG-PU-PEG and PEG-PEU-PEG have been proven to be biodegradable(Table 1).

TABLE 1 Degradation of PEG-PSeHDI-PEG and PEG-PSeSuHDI-PEG PBS E* (400U/mg) 7 days 14 days 7 days 14 days Mw DP Mw DP Mw DP Mw DP PEG- 6,2031.7  6,230 1.71 6,048 1.75 5,998 1.78 PSeHDI- PEG Mw 6,211 DP 1.70 PEG-9,479 1.79 9,312 1.72 7.970 1.7  8,891 1.8  PSeSuHDI- PEG Mw 9,824 DP1.69 *E is cholesterol esterase from bovine pancreas (one unit willhydrolyze 1.0 nmol of cholesteryl oleate to cholesterol and oleic acidper minute at pH 7.0 at 37° C.)

Example 2

To overcome perceived drawbacks in current ocular drug products, weconceived therapeutic agent-conjugated reverse thermal gels whichundergo temperature triggered sol-gel phase transition and form a gel atphysiologically important temperature. Since the therapeutic agentsconjugated reverse thermal gels can form gels by a simple injection inthe vicinity of target area, loss of therapeutic agents can beminimized. We hypothesize that controlled release will sustain thevitreous concentration of the therapeutic agents in the therapeuticrange longer with reduced side effects and treatment frequency (FIG. 6)achieving higher therapeutic indices. The specific aim is to control therelease of therapeutic agents using a functionalized reverse thermal gelthat gels upon reaching body temperature. We will control the releaserate by varying the affinity between the gel and the therapeutic agents.We will design the density of the delivery system to approximately matchthat of the vitreous fluid.

FIG. 6 shows simulated concentration profile of the therapeutic agentsin the vitreous fluid. (A) Proposed method that offers controlledrelease and a sustained concentration in the therapeutic range for along period after one injection. (B) Current method that needs frequentinjections.

Because affinity is the main factor for the conjugations, most types oftherapeutic agents can be conjugated to reverse thermal gels includingantiangiogenic agents for macular degeneration, antibiotics for virulentinflammation, and growth factors for ocular wound healings.

Synthesis of Reverse Thermal Gel and Conjugation to Therapeutic Agents:

We have recently designed and synthesized a biocompatible andbiodegradable reverse thermal gel, PEG-Poly(serinol urethane)-PEG. Thispolymer gels at around 32° C. The gel will be synthesized usingN-Boc-serinol, hexamethylene diisocyanate and poly(ethylene glycol) asoutlined in FIG. 1. The structure of this triblock copolymer is shownbelow.

This copolymer is treated with 50% (v/v) of trifluoroacetic acid todeprotect the primary amine groups and produce ammonium groups.Therapeutic agents are mixed with 10, 15 and 20% (wt) of theammonium-containing triblock copolymer in 0.2 ml of PBS. The negativelycharged therapeutic agents, due to carboxylic acid groups, are complexedwith positively-charged ammonium-containing triblock copolymer in theneutral solution by Coloumbic interaction. The affinity betweentherapeutic agents and the delivery polymer can lead to controlledrelease. The thermal behavior of therapeutic agent-complexed triblockcopolymer is studied rheologically at the temperature range of 25-45° C.

Determination of Loading Efficiency:

The mixture of therapeutic agents and ammonium-containing triblockcopolymer in PBS is raised to 37° C. to form a gel. 100 μl of PBS isadded on top of the gel and agitated gently on an orbital shaker. Theconcentration of therapeutic agents in the supernatant is determinedspectrophotometrically and chromatographically. The loading efficiencyis calculated by the comparison of total concentration to supernatantone.

Biocompatibility and Biodegradability:

Previously we have studied in vitro biocompatibility andbiodegradability of the composition Biocompatibility studied accordingto ISO 10993-5 guidelines revealed excellent biocompatibility. In thepresence of cholesterol esterase, the molecular weight of the polymerdecreased 25% in 45 days. In PBS without any enzyme, the decrease was2.5% in 45 days. The biocompatibility and biodegradability of thecompositions are investigated in vivo using New Zealand white rabbits. A0.5 ml of 20% therapeutic agent-complexed triblock copolymer solution isinjected subcutaneously into four spots in the upper and lower back onboth sides of the animal. In addition, the animals will receive 1injection of 0.05 ml of 20% therapeutic agent-complexed triblockcopolymer in the anterior segment of the eye. Biocompatibility also istested in the posterior segment of the eye if the anterior tests showpromising results. Rabbits are chosen to facilitate future efficacy andsafety tests including intraocular pressure tests. The animals areeuthanized at 1, 3, 7, 14 and 30 days. At each time point, the cutaneousand subcutaneous tissues surrounding the injection site are harvested.The tissues are fixed, stained, and examined by standard histologicalanalysis for any signs of acute and chronic inflammation. Control issaline solution. For biodegradability evaluation, the size and dryweight of the therapeutic agent-complexed triblock copolymer gel ismeasured and compared to the original size and weight.

Control the Release of Therapeutic Agents:

The amount of therapeutic agents released is periodically measuredspectrophotometrically and chromatographically in vitro using anartificial vitreous fluid. The release kinetics is measured at 37° C. ina custom made device (FIG. 7) with two compartments that mimic the eyeand the body. The device will be kept under sterile conditions. The 2liter PBS bath mimics the body. The plastic capsule mimics the eye. Thedialysis membrane of the capsule allows mass transfer that simulates themass transfer between the eye and the body. The device is filled with7.5 ml (the volume of an adult eye is 7.2 to 7.5 ml) of artificialvitreous fluid. A 0.2 ml of the therapeutic agent-complexed triblockcopolymer solution at ambient temperature is injected through thesampling port. Aliquots of the artificial vitreous fluid will beanalyzed periodically between 1 and 120 days. FIG. 7. (Left) The devicefor the study of the controlled release of therapeutic agents. (Right)the detailed cross-sectional view of the capsule.

Example 3 Nerve Repair

When nerves are damaged slightly they can self-regenerate. However whenthe nerve defects or gaps are greater than 2 cm, surgical managementwill be a significant challenge. Many researchers have studied nerveregeneration by autologous grafts and tubular conduits, and biomaterialsin which neurotransmitter, neural stem cell, and peptide are combined.These biomaterials are natural polymers such as collagen, fibrin,chitosan, and alginate and synthetic polymers. When these biomaterialsare implanted into injured sites, most of them interact with invadingneural cells by providing structural support, promote and eventuallyguide nerve growth (See, Yao, L., et al. Journal of Biomedical MaterialsResearch Part A, J Biomed Mater Res A. 2010 February; 92(2):484-92; Gao,J., et al. Proc. Nat'l. Acad. Sci., U.S.A., Vol. 103, No. 45 (Nov. 7,2006), pp. 16681-16686; and Mahoney, M J, et al. Biomaterials 27 (2006)2265-2274). In one example, a composition described herein is depositedat a nerve growth site, such as a site of trauma to a nerve, so that itcan serve as a nerve guide or scaffold for nerve regeneration.

Example 4 Treating Macular Degeneration with Anti-Angiogenic ReverseThermal Gel

Age-related macular degeneration (AMD) causes yellow deposits in themacula in the dry form, or choroidal neovascularization (CNV) andprofound vision loss in the wet or exudative form. As the leading causeof the blindness in individuals older than 55 years, AMD affects morethan 1.75 million people in the US and the number is expected toincrease to 3 million by 2020. Current treatments for wet AMD rely onphotodynamic therapy and injections of anti-angiogenic agents such asLucentis, Avastin, or Macugen. Photodynamic therapy (PDT) is based onthe effect of oxygen radicals on the choroidal neovascular capillaries,where the dye is preferentially bound. However, PDT is only effectivefor some types of CNV and rarely improves vision. The current standardof practice is anti-angiogenic therapy based on the inhibition ofvascular endothelial growth factor-A (VEGF-A) using the antibody(Avastin) or antibody fragment (Lucentis). However, because thehalf-life of protein-based drugs is short, the intravitreal injectionsare repeated frequently, sometimes monthly over several years. Thiscreates a substantial treatment burden, requiring multiple injectionsand follow-up visits.

We propose to ameliorate this burden using a controlled release platformthat can achieve a sustained therapeutic vitreous concentration ofanti-VEGF for a long period of time. This will reduce treatmentfrequency, increase patient compliance and achieve a higher therapeuticindex. The specific aim of this project is to control the release ofanti-angiogenic agents using a transparent, biocompatible reversethermal gel that gels upon reaching body temperature.

Synthesis of Reverse Thermal Gel

We have created a reverse thermal gel, PEG-Poly(serinol urethane)-PEG,a.k.a. ESHU (Scheme 1), using N-Boc-serinol, hexamethylene diisocyanateand poly(ethylene glycol).

We examined the chemical structures of ESHU by 1H FTNMR analysis (FIG.1). The methylene protons in PEG (a) and N-BOC-serinol (d) wereconfirmed at 3.65 and 4.0-4.2 ppm, respectively. The methylene protonsadjacent to nitrogen in urethane functional groups (e) were observed at3.17 ppm. The urethane protons bound to nitrogen and N-BOC-amine (b, c)were confirmed at 4.85-5.25 ppm. The signal at 1.42 ppm was assigned tomethyl protons in BOC.

Thermal Behavior of Copolymer:

The solution of ESHU showed phase transition from solution to geldepending on temperature as well as concentrations. The solutionremained gel (blue area) at body temperature in all testedconcentrations (FIG. 9 (A)). The consistent storage modulus (G′) of ESHUindicates that the solution remained fluidic below 30° C. The sharpincrease in G′ between 32-40° C. indicates gelation (FIG. 9 (B)).

In Vitro Biodegradability and Biocompatibility:

For biodegradability, ESHU was incubated in PBS and cholesterol esterasesolution at 37° C. Degradation was determined by comparison of themolecular weights. ESHU showed a very slow degradation (2.5% in 45 days)in PBS, however, it was accelerated by cholesterol esterase (22% in 45days) (FIG. 10).

In vitro biocompatibility was examined using primary bovine cornealendothelium cells. The cells were exposed to control (serum-free DMEM)and 15% (wt) ESHU gel in DMEM for 24 hr. The cells treated with CalceinAM showed no evidence of altered cellular morphology on microscopicexamination (FIG. 11, A and B). The viability was evaluated byimmunofluorescent microcropy after staining with propidium iodide andHoechst (FIG. 11, C and D). Cytotoxicity was calculated as propidiumiodide nuclei/total nuclei. No significant damage to cultured cells byESHU was observed compared to the control (P>0.05, two way ANOVA).

In Vivo Biocompatibility:

We tested in vivo biocompatibility in Sprague Dawley rats. We used nearsaturation concentration of ESHU (60% wt) to study the most severe hostresponse. Subcutaneous implantation in rats revealed a well toleratedinflammatory response with moderate amount of ED-1 positive macrophagesin the early stages, which largely resolved 4 weeks post-implantation(FIG. 12) indicating ESHU was biocompatible.

In Vitro Release of Avastin:

We chose Avastin (Bevacizumab) to represent antiangiogenic agentsbecause it is the most widely prescribed AMD treatment as it isinexpensive and effective. The release tests were performed in 7.5 ml of1% (wt) hyaluronic acid solution at 37° C. to mimic vitreous fluid andunder gyroscopic shaking to mimic human eye motion. Four formulas, 15and 20% (wt) ESHU with 0.5 and 1 mg Avastin were used. The solutiongelled immediately into a sphere upon injection into the 37° C.hyaluronic acid solution and quickly sank to the bottom indicating thedelivery system will be out of the optical axis of the eye. The releaseof active Avastin was measured by enzyme-linked immunosorbent assay(ELISA) according to manufacturer's protocol. The release is sustainedand nearly linear without reaching plateau during the 14-weekobservation period post injection (FIG. 13). The release was moresustained at higher concentration because ESHU formed a more rigid gelat higher concentration. The half-life of free Avastin in eyes is on theorder of 7 to 10 days. The window of therapeutic concentration mostlikely depends on local conditions, such as the presence of blood orfluid in the neovascular complex, and the state of the vitreous gel intowhich the drug is injected. Therefore, the Avastin-ESHU delivery systemhas three advantages over direct injection in that: 1. The therapeuticwindow is much longer, 2. The release is sustained, and 3. The injectionfrequency is greatly reduced.

Example 5 IKVAVS (SEQ ID NO: 21) Conjugated Reverse Thermal Gel PromotesNeurite Outgrowth Experimental Methods Synthesis of Reverse Thermal Gel

Reverse thermal gel was synthesized. N-BOC-serinol (0.5 g, 2.62 mmol)was dissolved in 1 ml anhydrous DMF in a 25 ml round bottom flask at 90°C. under a nitrogen atmosphere. HDI (0.44 g, 2.62 mmol) was added slowlyand the polymerization was performed. After 48 h, HDI (22 mg, 0.131mmol) was added to facilitate the reaction. The polymerization wasperformed for 2 days. More HDI (0.88 g, 5.24 mmol) was added and thereaction mixture was stirred for 12 h. After cooling down to ambienttemperature, the mixture was precipitated in excess anhydrous diethylether. The polymer was dissolved again in 2 ml anhydrous chloroform andpoured into excess anhydrous diethyl ether to precipitate out thepolymer. The purification process was carried out twice and theprecipitates were washed in 100 ml of anhydrous diethyl ether overnightto remove unreacted HDI. The intermediate was obtained after drying at45° C. under vacuum. As synthesized intermediate (1 g) and PEG (3 g, Mw:550) were dissolved in 2 ml anhydrous DMF in a 25 ml round bottom flaskand the reaction was performed at 90° C. for 12 h under a nitrogenatmosphere. After cooling down, the mixture was precipitated into excessanhydrous diethyl ether. After drying, the polymer was further purifiedwith dialysis membrane in water at room temperature for 3 days. Thedialyzed solution was freeze-dried and a transparent reverse thermal gelwas obtained.

Conjugation of IKVAVS (SEQ ID NO: 21)

De-protection of reverse thermal gel: As synthesized gel (100 mg) wasdissolved in 10 ml chloroform in a 50 ml round bottom flask. TFA (10 ml)was added and BOC de-protection was performed for 1 h at roomtemperature. After removing TFA and chloroform by rotary evaporation,the polymer was purified using dialysis in water at room temperature for2 days. The dialyzed solution was freeze-dried and a pale yellowishsolid (NH₂-GEL) was obtained.

Synthesis of IKVAVS (SEQ ID NO: 21) Conjugated Reverse Thermal Gel(IKVAVS-GEL):

I(BOC)K(BOC)VAVS(tBu)-OH (83 mg, 0.095 mmol) was dissolved in 23 mlanhydrous DMF in a 50 ml round bottom flask. DCC (21.6 mg, 0.105 mmol)solution in 1 ml anhydrous DMF was added slowly at 0° C. NH₂-GEL (50 mg,0.19 mmol NH₂) solution in 1 ml anhydrous DMF was added with a catalyticamount of DMAP, which was stirred for 24 h at room temperature under anitrogen atmosphere. After 24 h, acetic anhydride (19.4 mg, 0.19 mmol)and pyridine (75.1 mg, 0.95 mmol) were added which was then stirred for24 h at room temperature. The cyclohexylurea was filtered off. Afterremoving 90% DMF using rotary evaporator, it was poured into excessdiethyl ether to precipitate out I(BOC)K(BOC)VAVS(tBu)-GEL. Afterdrying, BOC was removed in 20 ml chloroform/TFA (50/50, v/v) mixture for1 h at room temperature. After removing TFA and chloroform using rotaryevaporator, the polymer was purified by dialysis in water at roomtemperature for 2 days. The dialyzed solution was freeze-dried and apale yellowish solid, IKVAVS-GEL, was obtained.

Cell Culture

Cells, SH-SY5Y (ATCC, CRL-2266), were cultured in DMEM/F12 (1:1) mediumwith 10% fetal bovine serum (FBS), and 1% antibiotics. The cells wereincubated in a humidified atmosphere with 5% CO₂ at 37° C. The mediumwas refreshed every three days until the cells reached 95% confluence.The cells were harvested from the petri dish by incubation in 1 ml oftrypsin solution (0.25%) for 5 min, neutralizing with 5 ml ofserum-supplemented medium, centrifugation and removal of supernatant.The cell pellets were resuspended in serum-supplemented medium and 5×10³cells was used immediately for 2D neuronal cell culture.

2D Neuronal Cell Culture

Fifty μl of each solution (15%, wt) of pure reverse thermal gel andIKVAVS-GEL was transferred into 96-well plate on 37° C. heating plate.After 5 min, cell suspension (5×10³ cells) in 150 μl of medium was addedon top of the gel. For a control, the same number of cell suspension in200 μl of medium was transferred into laminin coated 96-well plate. A100 μl of medium was refreshed every two days. The cell growth wasexamined on a microscope. After 7-day culture, 10 μM of retinoic acid(RA) was added and neurite outgrowth was monitored on a microscope.

Results 3D Structure of IKVAVS-GEL

To examine 3D structure of IKVAVS-GEL, 15% gel solution was placed in37° C. water bath. Immediately after the gelation, it was placed inliquid nitrogen, frozen, and lyophilized. After drying, 3D structure wasexamined by SEM. Both the macro and micro pores were observed and theywere interconnected each other (FIG. 14) which are good conditions forcell migration and nutrient supply.

2D Cell Growth and Neurite Outgrowth

Cells attached very well on laminin surface, a positive control, and fewfloating cells were observed (FIG. 15A). After 7-day culture, cells grewas clusters and formed many clumps which are typical morphology ofgrowing SH-SY5Y (FIG. 15B). At day 7, 10 μM of RA (final concentration)was administered in one group and the differentiation of cells wascompared after 14-day culture. Interestingly, some short neuriteoutgrowth was observed in a group without RA (FIG. 15C). However, muchdense and longer neurite outgrowth was observed with RA (FIG. 15D).

Thus, laminin surface provided a good environment not only for cellgrowth but neurite outgrowth.

Cells seeded on pure reverse thermal gel did not attach well on thesurface. Since the surface did not provide any bioactive cue, cellsrather aggregated together (FIG. 16A) and slowly migrated from theaggregates (FIG. 16B). The differentiation was also not as extensive asthe one on laminin surface. A few neurite outgrowth was observed withoutRA (FIG. 16C). And they were not extended well even with RA (FIG. 16D).Thus, pure reverse thermal gel surface did not seem to provide a goodenvironment for cell attachment and neurite extension. On the contrary,cells seeded on IKVAVS-GEL surface showed as good morphology and neuriteoutgrowth as on laminin surface. Cells attached well on the surface anddid not form a big aggregate as pure reverse thermal gel (FIG. 17A).They formed many clumps after 7-day culture as seen on laminin surface(FIG. 17B). Neurite outgrowth without (FIG. 17C)/with (FIG. 17D) RA weremuch better than that on pure reverse thermal gel which is comparablewith laminin surface. Thus, IKVAVS (SEQ ID NO: 1) conjugated reversethermal gel provided a good cue for cell attachment and promoted neuriteoutgrowth.

Example 6 Transplantation of IKVAVS (SEQ ID NO: 21) Conjugated ReverseThermal Gel Promotes Axon Regeneration and Functional Recovery after aThoracic Spinal Cord Contusion in Adult Rats Aim:

To determine the number of neurons with an axon projecting beyond athoracic spinal cord contusion and hind limb motor performance aftertransplantation of IKVAVS (SEQ ID NO: 21) conjugated reverse thermalgel.

Hypotheses:

IKVAVS (SEQ ID NO: 21) conjugated reverse thermal gel promotes axonalregeneration in the contused adult rat spinal cord, and recovery ofhindlimb motor function after a contusion of the rat thoracic spinalcord is proportional to the number of regenerated axons into the caudalcord.

Model:

IKVAVS (SEQ ID NO: 21)-conjugated reverse thermal gel is transplantedinto a 3-day old contusion in the adult rat T9 spinal cord. Control ratsreceive ESHU or ‘medium’. Survival is determined 1, 2, 4, and 8 weeksafter transplantation. Biocompatibility, anatomical changes, cellularresponses, axon regeneration, and motor function is investigated.

Methods Rats:

Adult female Sprague Dawley, 180-200 g. Total number of rats is 63.Three groups are as follows: pure reverse thermal gel, IKVAVS (SEQ IDNO: 21) conjugated reverse thermal gel, and medium only, with 20 ratseach (n=3 for 1, 2, and 4 weeks; n=12 for 8 (+1) weeks).

Contusion:

T9; 1H-impactor at 200 kDyn.

Implantation:

Five (5) μL pure reverse thermal gel, IKVAVS (SEQ ID NO: 21) conjugatedreverse thermal gel, or medium into mid-point of 3-day old contusion.

Survival:

1, 2, 4, and 8 (+1 for tracing) weeks after transplantation.

Motor Testing:

Only in 8 (+1) week survival group. BBB (includes BBB-subscore) (before(3 times) and 1, 3 days after injury, and 3, 7 days, and then weeklyafter transplantation); foot print and horizontal ladder walking (before(3 times) and 3 days after injury, and 3 days and 1, 2, 4, 8 weeks aftertransplantation).

Retrograde Tracing:

At 8 weeks after transplantation, 1.2 μl 2% FB is injected in the spinalcord 7 mm caudal to the contusion epicenter.

Histology:

4% paraformaldehyde fixation. Cryostat sections of spinal cord(transplant plus 5 mm rostral and distal cord: 20 μm, horizontal, 10series) and brainstem and cerebral cortex (40 μm, transversal, 10series).

Analyses (*=Main Outcome Measures. Others are to Support)

Analysis of Axon Regeneration:

-   -   1. Quantify FB-labeled neurons in spinal cord rostral to        transplant, brainstem, cortex.    -   *2. Quantify serotonergic and dopaminergic axons caudal to        transplant.

Analysis of Motor Function:

-   -   *1. Overground locomotion (BBB)+higher motor functions (BBB        subscore).    -   *2. Sensorimotor performance (horizontal ladder walking).    -   *3. Locomotion pattern: stride length, base of support, and        angle of rotation (foot print).

Analysis of Cellular Changes:

-   -   1. Scar (ICC for astrocytes and CSPG)    -   2. Cell architecture (Nissl staining).    -   3. Neuron presence (ICC for NeuN)    -   4. Inflammation (ICC for macrophages)

Analysis of Anatomical Changes:

-   -   1, Tissue sparing (using Nissl-stained sections).        *=main outcome measures. Others are to support.

Example 7 Testing of Intraocular Dosage Form in Rabbits

Human eyes are often exposed to various risks of ocular diseases. Theycan be an age-related such as macular degeneration; virulentinflammations by foreign bodies such as endophthalmitis; and systemicside effects such as diabetic retinopathy, macular edema, and retinalvein occlusion. Intravitreal drug injections are the most effective wayto maximize drug concentrations in the eye and reduce the loss whereaslimiting systemic exposure. However, the effective management of chronicocular conditions requires long-term frequent local administrations withover- and underdoses. Those repeated intravitreal injections are notonly invasive and inconvenient for patients, but they may also greatlyincrease the risk of complications such as intraocular pressureelevation, cataracts, and retinal detachment.

To overcome these drawbacks therapeutic agents are conjugated withreverse thermal gels (TA-ESHU) which undergo temperature triggeredsol-gel phase transition and form a gel at body temperature. Since theTA-ESHU can form gels by a simple injection in the vicinity of targetarea, the loss of therapeutic agents can be minimized. The controlledrelease sustains the vitreous concentration of the therapeutic agents inthe therapeutic range longer with reduced side effects and treatmentfrequency achieving higher therapeutic index. The release rate iscontrolled by varying the affinity between the gel and the therapeuticagents. The density of the delivery system is designed to approximatelymatch that of the vitreous fluid.

Sample sizes are selected based on a power analysis with a significancelevel a of 0.05 and a power (1−β) of 0.85. Assuming a typical standarddeviation of 35% and desiring to detect a 33% difference in means, weobtain a sample size of 10 using MiniTab (Statistical Software). In caseour standard deviation assumption is proven to be invalid a posteriori,we will employ an adaptive sampling rate for the testing.

Therapeutic agent-conjugated polymer compositions are injected in threeseparate parts of the animal's eye, upper back, and lower back. Eachpart has two samples. For eye, a left eye and a right eye. For upperback, a left side and a right side. For lower back, a left side and aright side. Then each animal has two samples for the biocompatibilityand biodegradibility. Five animals are used for each time point. Then,the sample size in each time point is 10 (5×2=10).

Preparation:

All rabbits are used after at least three days post arrival. For eachgroup of experiment: 5 survival times×6 rabbits/survival time (5 fortest, 1 for control)=30 rabbits.

Pre-Operative Evaluation and Preparation:

Pre-op evaluation and preparation includes weighing the rabbit andrecording the body weight.

For Biocompatibility Experiment Through Intravitreal Injection:

0.05 ml of 20% and 30% therapeutic agent-conjugated reverse thermal gelsolution will be injected in the eye. In one example, the therapeuticagent is Avastin. Typically the injection of thermal gel has been doneunder anesthesia condition for intravitreal injection. Rabbits areanesthetized using either sodium pentobarbital or a mixture of ketamineand xylazine. The volume of thermal gel for intravitreal injection hasbeen in the range of 50-100 μl. The minimum volume (50 μl) is injected.A 25 gauge needle is used for the injections. After euthanization with120 mg/kg sodium pentobarbital at 1, 3, 7, 14 and 30 days, the surgicaleye including the upper eyelids are removed. The surgical eye is fixedin 4% formaldehyde, stained, and examined by standard histologicalanalysis for any signs of acute and chronic inflammation. Control is0.05 ml of saline solution.

For Intraocular Pressure (IOP) Measurement:

The measurement of IOP is performed preinjection and at 1, 3, 7, 14 and30 days post-injection using tonometer by distributor's protocol.

At the end of the experiments cells are isolated for futurebiocompatibility and stromal cell differentiation capability tests oftherapeutic agent-conjugated reverse thermal gels as follows.

Animals are euthanized following survival times and tissue and cells areharvested.

The rabbits are examined and its response to gentle palpation orhandling of any presumed painful areas (e.g., the site of surgery) isassessed. The rabbit is weighed every 24 hours, and the cage is examinedfor signs of normal or abnormal urination or defection.

The following criteria will be sued to determine full recovery fromsurgery: 1) locomotive and grooming behavior equivalent to presurgicalstate, and 2) eating and drinking equivalent to presurgical state.Postoperative analgesia will be provided by injections of Ketoprofen 12hours after surgery, and once per two days afterward (if needed).Rabbits will be monitored closely (every 12 hours) for any signs ofdistress (vocalization, decrease in food consumption, etc.). If rabbitsscratch or bite their injection sites, if the skin becomes reddened orif dermatitis develops, or rabbits lose more than 20% of their immediatepost-operative body weight, they will be euthanized. Body weight will bemonitored every 24 hours.

For intravitreal injection, some clinical signs may appear when animalsreceive injections, such as scratching their injection sites, increasein intraocular pressure, weight loss. Complications are not expected inany case. If rabbits keep scratching their intravitreal injection sites,if the intraocular pressure keeps increasing, or rabbits lose more than20% of their immediate post-operative body weight, they are euthanized.Body weight is monitored every 24 hours.

Example 8 Spinal Cord Injury A. Transection

To determine the reverse thermal gels' efficacy in functional nerveregeneration, 10 rats per time point are used because this is theminimum number needed in order to obtain meaningful data. Histological,behavioral, and electrophysiological assessment is performed at 2, 5,and 8 weeks for spinal cord regeneration after surgery. If 10 animalsare used per condition, then 30 animals are necessary to fulfill thestudy (3×10=30). 10 rats are used per condition. Power analysis isperformed using MiniTab Software (Statistical Software). Ten types ofpolymer composition are tested, so 300 animals are necessary to fulfillthe study (10×30=300).

Negative control is “injury only” for CNS nerve regeneration. Positivecontrols are not appropriate for the following reasons. There is nocurrent treatment that can lead to functional recovery, so there is nopositive control. Therefore, two groups of 20 rats in total are requiredfor the first time experiment, therefore 320 animals are necessary tofulfill the study (10×30+20=320). A total of 60 animals (three timepoints, 10 animals/time point) for each polymer conduit will besacrificed at three time points for histological, behavioral, andelectrophysiological assessment on nerve regeneration.

Preparation:

All animal are used after at least three days post arrival. The animalsare prepared by removing hair from the surgical site, and the surgicalsites are sterilized with an appropriate skin disinfectant such asBetadine. For each experiment: three survival times×10 animals/survivaltime are used, totaling 30 animals. Pre-operative evaluation andpreparation includes weighing the animal and recording the body weight.Aseptic surgical technique is ensured by performing the surgeries in adisinfected suite.

For Direct Spinal Cord Injury:

-   -   1. The rats are anesthetized using sodium pentobarbital (45-50        mg/kg) given either intraperitoneally (using a 25-26 gauge        needle) under brief anesthesia induced with 5% isofluorane.    -   2. Opthalmic ointment is used on the eyes to prevent corneal        abrasion.    -   3. The hair down the back over the spine is removed with        electric clippers.    -   4. The area is cleaned with chlorhexaderm and then with 70%        ethanol.    -   5. The rat is draped with sterile surgical drapes.    -   6. An incision is made over the thoracic region of the spinal        cord T6-T11.    -   7. The muscle is cut on both sides of the spine.    -   8. A double laminectomy is performed removing T9 and T10.    -   9. The dura mater is excised longitudinally.    -   10. To sever the dorsal corticospinal tracts, microscissors        previously marked at 1.5 millimeters are used to cut down        through the dorsal columns until we reach the pre-determined        depth. The length of the cavity is 2 millimeters.    -   11. The reverse thermal gel is injected into the lesioned        cavity.    -   12. In order to stop bleeding during surgery, Tisseel Fibrin        Sealant, a product made by Baxter, is applied. It is sterile and        non-pyrogenic. The literature contains many references to the        use of this product in rats indicating that it is safe and        effective in this species. Tisseel is mixed according to package        directions and applied topically to bleeding areas during        surgery. No side effects are expected.    -   13. The dura is sutured and the muscle and skin will be closed        in layers.    -   14. The rat recovers on a heating pad or under a heat lamp.    -   15. Animals are monitored for up to 8 weeks. These rats are        expected to maintain the ability to urinate and defecate on        their own without having a person manually express. The rats        also are expected to be able to walk around on their fore and        hind limbs on their own accord; however, in the first 48 hours,        they are expected to go through spinal shock and should not be        able to have full use of their hind limbs.    -   16. Ketaprofen is administered post-operatively for pain that        the rat may experience if needed.    -   17. Suture and/or wound clips are removed 10-14 days        post-operatively).

Rodent Euthanasia and Tissue Harvest:

Following post-inoculation survival times of each time point, theanimals are be anesthetized with 50 mg/kg sodium pentobarbitalintraperitoneally, and tissue is harvested and transfer into bufferedaldehyde solution. Tissue will be harvested after complete euthanasia.

B. Compression

Alternately, another spinal cord injury model is performed according tothis protocol. No other change is made to this protocol. In the originalprotocol, we will use transection to create spinal cord injury. Here, wedescribe an alternative spinal cord injury model to transection: a clipcompression method is used to create spinal cord injury as the secondmodel in the protocol. Because the “transection procedure” is expectedto cause more severe injury to spinal cord as compared with “compressioninjury model”, we evaluate the effect of polymers through “compressioninjury model” at first, then two of the most effective polymers arechosen for the evaluation in “transection model”. Like the firstprotocol, three time points are set, with ten rats per time point,totaling 60 rats for this modified protocol.

In the surgical procedure, a 30-40 mm dorsal midline incision is madeand laminectomy is performed at T6-T11 level. Compressive injury isproduced by transient extradural application of a modified iris clip,which exerted a force of about 90 gram on the spinal cord for 2 min.After removal of the clip, the dura in the lesion area is incised, andspinal cord is exposed, then the prepared polymer is administered in thelesion. Dura and skin incision is closed, and the animal is returned tocages with highly absorbent soft bedding in pairs (to reduceisolation-induced stress).

No particular animal injury model of human spinal cord injury completelymimics all clinical aspects of human patients. The use of multipleinjury models has greatly advanced our understanding of thepathophysiology, so we use both the transection method because it causes100% nerve damage and should be more controllable in terms of nervedamage than partial injury model such as contusion or compression.However, transection injury method is very different from most ofclinical SCI cases. Most SCI cases are caused by automobile and sportsaccidents, and gunshot wounds. Contusion and compression injury modelsmore closely mimic the conditions in these clinical cases. Of contusionand compression models, the latter may be preferred because it isquicker and simpler to apply.

Immediately following surgery and during recovery from anesthesia, ratsrecover under a heat lamp to raise the recovery area ambient temperatureto between 85-90° F. Each animal is examined and assessed for itsresponse to gentle palpation or handling of any presumed painful areas(e.g., the site of surgery, the site of lesion). The animal is weighedevery 24 hours, and the cage is examined for signs of normal or abnormalurination or defection.

The following criteria is used to determine full recovery fromsurgery: 1) locomotive and grooming behavior equivalent to presurgicalstate, and 2) eating and drinking equivalent to presurgical state.Postoperative analgesia is provided by injections of Ketoprofen 12 hoursafter surgery, and once per two days afterward. Animals are monitoredclosely (every 12 hours) for any signs of distress (vocalization,decrease in food consumption, etc.). Furthermore, the health of theanimals following surgery is monitored for adverse signs due to theeffects of the injured nerves. If rats scratch or bite their implants,if they lose hair over their implants, if the skin becomes reddened orif dermatitis develops, if incisions do not heal or an exudate developsor rats lose more than 20% of their immediate post-operative bodyweight, they are euthanized.

Having described this invention, it will be understood to those ofordinary skill in the art that the same can be performed within a wideand equivalent range of conditions, formulations and other parameterswithout affecting the scope of the invention or any embodiment thereof.

1. A reverse thermal gel composition comprising a triblock copolymer, ora pharmaceutically acceptable salt thereof, having the structure B-A-Bin which A is one of a polyurethane or poly(ester urethane) group thatcomprises one or more pendant active groups, blocked active groups oractive agents and B is a hydrophilic block, wherein the composition is agel at 35° C.-40° C. and a liquid solution at a lower temperature. 2.The composition of claim 1 in which A is a copolymer of a diol and adiisocyanate.
 3. The composition of claim 2 in which the diol is anamino-substituted or N-substituted serinol in which the N is substitutedwith one of a hydrogen, a protective group, or an active agent.
 4. Thecomposition of claim 3 in which the N of the N-substituted serinol is—NHR in which R is a protective group.
 5. The composition of claim 4 inwhich R is selected from the group consisting of carbobenzyloxy;p-methoxybenzyl carbonyl; tert-butyloxycarbonyl;9-fluorenylmethyloxycarbonyl; benzyl; p-methoxybenzyl;3,4-dimethoxybenzyl; p-methoxyphenyl; tosyl; nosyl(4-nitrobenzenesulfonyl) and 2-nitrobenzenesulfonyl.
 6. The compositionof claim 4 in which R is tert-butyloxycarbonyl.
 7. The composition ofclaim 2 in which the diol comprises one or more ester groups.
 8. Thecomposition of claim 7 in which the diol is a reaction product of acyclic anhydride and a diol comprising one or more pendant activegroups, blocked active groups or active agents.
 9. The composition ofclaim 8 in which the diol is the reaction product of succinic anhydrideand the diol is an N-substituted serinol in which the N is substitutedwith one of a hydrogen, a protective group, or an active agent.
 10. Thecomposition of claim 2 in which the diol comprises a pendant amino groupor an amine.
 11. The composition of claim 2, in which the diisocyanateis hexamethylene diisocyanate (1,6-diisocyanatohexane).
 12. Thecomposition of claim 1, comprising a copolymer comprising the structure:

in which R1 is H or a protective group, R2 is isocyanate or—NC(O)-polyethylene glycol (—NC(O)-PEG) and n is greater than
 5. 13. Thecomposition of claim 1, comprising a copolymer comprising the structure:

in which R1 is H or a protective group, R3 is PEG and n is greater than5.
 14. The composition of claim 1, comprising a copolymer comprising thestructure:

in which R1 is H or a protective group or an active agent, R2 isisocyanate or NC(O)-PEG and n is greater than
 5. 15. The composition ofclaim 1, comprising a copolymer comprising the structure:

in which R1 is H or a protective group, R3 is PEG and n is greater than5.
 16. The composition of claim 1, the triblock copolymer having anaverage molecular weight of between about 5,000 and 10,000 Da (Daltons),excluding, when present, the molecular weight of the active agent. 17.The composition of claim 1 in which A is one of a polyurethane orpoly(ester urethane) group that comprises one or more pendant charged oractive groups.
 18. The composition of claim 17 in which the one or morependant charged or active groups is —NH₂.
 19. The composition of claim18 in which the NH₂ is covalently linked or non-covalently bound to oneor more active agents or biologically functional groups.
 20. Thecomposition of claim 18 in which the NH₂ is linked to an extracellularmatrix (ECM) epitope.
 21. The composition of claim 18 in which the NH₂is linked to a functional entity that aids in evasion of an immuneresponse.
 22. The composition of claim 1 in which the active agent is anoligopeptide selected from the group consisting of IKLLI (SEQ ID NO: 1),REDV (SEQ ID NO: 2), LDV, RGDSP (SEQ ID NO: 3), RGDV (SEQ ID NO: 4),LRGDN (SEQ ID NO: 5), RGDT (SEQ ID NO: 6), YIGSR (SEQ ID NO: 7), TTSWSQ(SEQ ID NO: 8), AEIDGIEL (SEQ ID NO: 9), WYRGRL (SEQ ID NO: 10), SIKVAVS(SEQ ID NO: 11), PDSGR (SEQ ID NO: 12), RNIAEIIKDI (SEQ ID NO: 13), DGEA(SEQ ID NO: 14), VTXG (SEQ ID NO: 15), PRRARV (SEQ ID NO: 16),YEKPGSPPREVVPRPRPGV (SEQ ID NO: 17), RPSLAKKQRFRHRNRKGYRSQRGHSRGR (SEQID NO: 18), RIQNLLKITNLRIKFVK (SEQ ID NO: 19), RGD, IKVAV (SEQ ID NO:20) and IKVAVS (SEQ ID NO: 21).
 23. The composition of claim 1 furthercomprising an active agent complexed to the triblock copolymer.
 24. Thecomposition of claim 23, in which the active agent is one ofbevacizumab, pegaptanib sodium and Ranibizumab.
 25. The composition ofclaim 23 in which the active agent is one or more of an antibiotic, ananti-inflammatory agent, an antiangiogenic agent, a hormone, a cytokine,a chemokine, and a growth factor.
 26. The composition of claim 23 inwhich the active agent is chosen from one or more of: pegaptanib sodium;lucentis; tryptophanyl-tRNA synthetase (TrpRS); AdPEDF; VEGF TRAP-EYE;AG-013958; bevacizumab; JSM6427; TG100801; ATG3; perceiva; E10030;ARC1905; colociximab; endostatin; vatalanib; pazopanib; sirolimus;bevasiranib; AGN211745; nepafenac; ketorolac tromethamine;acetaminophen; bromfenac; ciprofloxacin; norfloxacin; afloxacin;levofloxacin; gentamicin; tobramycin; neomycin; erythromycin;trimethoprim sulphate; polymixin B; ganciclovir and fomivirsen.
 27. Thecomposition of claim 1, in which the triblock copolymer is one of:

in which R1 is H and R3 is PEG, complexed with an antiangiogenic agent.28. The composition of claim 27 in which the antiangiogenic agent is oneof bevacizumab and pegaptanib sodium.
 29. The composition of claim 1 inwhich B is selected from the group consisting of PEG; hyaluronan;poly(vinyl alcohol; oligo(vinyl alcohol); a poly(electrolyte); anoligo(electrolyte); and a polycarbohydrate.
 30. The composition of claim1 in which B is a polyethylene glycol.
 31. A method of delivering anactive agent to a patient, comprising delivering to the patient areverse thermal gel composition comprising an active agent and atriblock copolymer having the structure B-A-B in which A is one of apolyurethane or poly(ester urethane) group that comprises one or morependant active groups, blocked active groups or active agents and B is ahydrophilic block and the composition is a gel at 37° C. and a liquid ata lower temperature. 32-33. (canceled)
 34. The method of claim 31 inwhich the active agent is one or more of an antibiotic, ananti-inflammatory agent, an antiangiogenic agent, a hormone, a cytokine,a chemokine and a growth factor.
 35. The method of claim 31 in which theactive agent is chosen from one or more of: pegaptanib sodium; lucentis;tryptophanyl-tRNA synthetase (TrpRS); AdPEDF; VEGF TRAP-EYE; AG-013958;bevacizumab; JSM6427; TG100801; ATG3; perceiva; E10030; ARC1905;colociximab; endostatin; vatalanib; pazopanib; sirolimus; bevasiranib;AGN211745; nepafenac; ketorolac tromethamine; acetaminophen; bromfenac;ciprofloxacin; norfloxacin; afloxacin; levofloxacin; gentamicin;tobramycin; neomycin; erythromycin; trimethoprim sulphate; polymixin B;ganciclovir and fomivirsen. 36-41. (canceled)
 42. The method of claim31, in which the composition is delivered to a patient's eye. 43-44.(canceled)
 45. A method of making a triblock copolymer, comprising: a.reacting a diol with a diisocyanate to produce a diol product; and b.attaching hydrophilic groups to the diol product.
 46. The method ofclaim 45 in which the hydrophilic groups are polyethylene glycol (PEG).47. The method of claim 45 in which the hydrophilic groups are selectedfrom the group consisting of PEG; hyaluronan; poly(vinyl alcohol);oligo(vinyl alcohol); and a polycarbohydrate.
 48. The method of claim 45further comprising synthesizing the diol by reacting a diol precursorwith a cyclic anhydride.
 49. The method of claim 48 in which the cyclicanhydride is succinic anhydride.
 50. The method of claim 45, in whichthe diol is N-serinol in which the N is substituted with a protectivegroup.
 51. The method of claim 49 in which the protective group is boc,such that the diol is N-boc-serinol.
 52. The method of claim 45 furthercomprising complexing the triblock copolymer with an active agent.53-54. (canceled)
 55. The method of claim 52 in which the active agentis one or more of an antibiotic, an anti-inflammatory agent, anantiangiogenic agent, a biologically functional oligopeptide, and agrowth factor.
 56. The method of claim 52 in which the active agent ischosen from one or more of: pegaptanib sodium; lucentis;tryptophanyl-tRNA synthetase (TrpRS); AdPEDF; VEGF TRAP-EYE; AG-013958;bevacizumab; JSM6427; TG100801; ATG3; perceiva; E10030; ARC1905;colociximab; endostatin; vatalanib; pazopanib; sirolimus; bevasiranib;AGN211745; nepafenac; ketorolac tromethamine; acetaminophen; bromfenac;ciprofloxacin; norfloxacin; afloxacin; levofloxacin; gentamicin;tobramycin; neomycin; erythromycin; trimethoprim sulphate; polymixin B;ganciclovir and fomivirsen.
 57. The method of claim 52 in which theactive agent is an oligopeptide selected from the group consisting ofIKLLI (SEQ ID NO: 1), REDV (SEQ ID NO: 2), LDV, RGDSP (SEQ ID NO: 3),RGDV (SEQ ID NO: 4), LRGDN (SEQ ID NO: 5), RGDT (SEQ ID NO: 6), YIGSR(SEQ ID NO: 7), TTSWSQ (SEQ ID NO: 8), AEIDGIEL (SEQ ID NO: 9), WYRGRL(SEQ ID NO: 10), SIKVAVS (SEQ ID NO: 11), PDSGR (SEQ ID NO: 12),RNIAEIIKDI (SEQ ID NO: 13), DGEA (SEQ ID NO: 14), VTXG (SEQ ID NO: 15),PRRARV (SEQ ID NO: 16), YEKPGSPPREVVPRPRPGV (SEQ ID NO: 17),RPSLAKKQRFRHRNRKGYRSQRGHSRGR (SEQ ID NO: 18), RIQNLLKITNLRIKFVK (SEQ IDNO: 19), RGD, IKVAV (SEQ ID NO: 20) and IKVAVS (SEQ ID NO: 21).
 58. Themethod of claim 52 in which the diol is N-serinol, in which the N issubstituted with a protective group.
 59. The method of claim 58 in whichthe protective group is boc, such that the diol is N-boc-serinol. 60.The method of claim 45 in which the diisocyanate is hexamathylenediisocyanate.
 61. The method of claim 45 in which the diol isN-boc-serinol. 62-65. (canceled)